Rubbers stabilized by a bis (2-hydroxy-3-alpha-alkyl-cycloalkyl-5-methylphenyl)-methene or salts thereof



United States Patent d ce RUBBERS STABILIZED BY A BIS(2-HYDROXY-3-a- ALKYL CYCLOALKYL 5 METHYLPHENYL)- METHENE 0R SALTS THEREOF Arthur Lambert and Boris Nicholas Leyland, Blackley, Manchester, England, assignors to Imperial Chemical Industries Limited, a corporationof Great Britain No Drawing. Application December 8, 1952,

' Serial No. 324,822

Claims priority, application Great Britain December 19, 1951 6 Claims. (Cl. 260--29.7)

This invention relates to improvements in the manufacture of age-resistant natural and synthetic rubbers and rubber articles.

We have found that bis-(Z-hydroxy-3-a-alkylcycloalkyl-S-methylphenyl)-methanes, in which the cycloalkyl group is a cyclopentyl, methylcyclopentyl, cyclohexyl or methylc'yclohexyl one and the alkyl substituent has not more than 4 carbon atoms and is attached to the a-carbon atom of the cycloalkyl group, i. e. the carbon atom which is joined to the phenyl radical are very valuable antioxidants for natural and synthetic rubbers.

The above mentioned compounds are new and'they are made according to the processes which are described in co-pending application No. 324,821, filed December 8, 1952.

The new compounds are, according to one process of the invention, manufactured in two stages. The first stage consists of combining, in the presence of an acid condensing agent, 1 molecular proportion of p-cresol with 1 molecular proportion of an alpha-alkylcyclopentene, methyl-alpha-alkylcyclopentene, alpha-alkylcyclohexene or methyl-alpha-alkylcyclohexene, in which the alkyl substituent has not more than 4 carbon atoms. In the second stage, 2 molecular proportions of the p-cresol derivative, i. e. 2-alpha-alkyl-cycloalkyl-4-methylphenol, which is obtained in the first stage, are condensed with one molecular proportion of formaldehyde or of a substance yielding formaldehyde, in the presence of an acid condensing agent.

We have also found that the normal and basic aluminium, barium, calcium, magnesium, strontium, and zinc salts of the above new compounds are likewise valuable antioxidants for natural and synthetic rubbers.

These salts, which are themselves new, may be made from the above new compounds according to known methods of salt formation.

Both the new compounds and their salts have not only excellent preservative properties in rubbers and produce little or no staining but they have excellent physical properties also which make them Well adapted for use in the mechanical processes employed in manufacturing rubber articles. They are also well adapted for addition to latices of both natural and synthetic rubber and for stabilising the latter.

The antioxidants are employed in the manufacture of rubber and rubber articles according to the usual methods. Thus they may for example be mixed with the rubber along With vulcanising and other ingredients and the resulting mixes then cured by heat treatment, or they may be mixed with rubber along with other compounding ingredients and the mixture vulcanized by treatment with sulphur monochloride in the cold. The antioxidants are effective in proportions of from about A to 2 per cent of the weight of the rubber.

The synthetic rubbers which may be used include for example polymers of butadiene-1z3, isobutene and 2- ch1oro-butadiene-1:3 and copolymers of either of these compounds with acrylonitrile, styrene, methyl methacry- 2,748,096 Patented M ay 29,1956

late and other well known polymerisable compounds which are used in the manufacture of these rubbers.

The following examples in which parts are by weight illustrate but do not limit the invention.

Example 1 Vulcanisable rubber stocks of the following compositions were prepared by the usual process of mixing using his (2 hydroxy 3 a methylcyclohexyl 5 methyl- .phenyD-methane as antioxidant and using also. no antioxidant.

The above antioxidant may be made according to the process of co-pending application No. 324,821, filed December 8, 1952. v

Mix A B Pale crepe natural rubber 100 100 Zinc oxide 10 10 Blane fixe 75 Stearie acid. 1 1 3 3 .5 0.5 1

Sheets of each mix were cured for 75 minutes at 141 C. and ageing tests carried out on the vulcanisates.

. The results of the ageingtests were as follows:

Unaged tensile strength (Kg/cm?) 196 191 Percent retained tensile strength after bomb ageing at 70 C. and 300 p.s.i. oxygen pressure:

8 days Per1shed. 51 12 day 38 16 days rln 34 Example 2 v Vulcanisable rubber stocks of the following compositions were prepared by the usual process of mixing using his (2 hydroxy 3 a methylcyclohexy 5 methylphenyl)-methane as antioxidant and using also no antioxidant.

Mix 0 D Pale crepe natural rubber 100 Zinc oxide"... 10 10 Blane fixe 75 75 Stearic acid 1 1 Titanium dioxide 10 i0 Sulphur. 2 2 Zinc diethyldithiocarbamate 0. 375 0. 375 Antioxidan 1 Sheets of each mix were cured for 12 minutes at C. and ageing tests carried out on the vulcanisates. Staining was also examined by exposure outdoors.

Example 3 This is similar to Example 2, as regards the mixes (except the antioxidants), the curing and the testing, but includes 4 separate sets of tests, each set having been performed separately. In each set there is one or more mixes with antioxidants and one without as shown in the following lists:

E. No antioxidant.

droxy 3 alpha alkyl cycloalkyl 5 methylphenyl)- methanes and the basic and normal aluminum, barium, calcium, magnesium, strontium and zinc salts of such methanes, the cycloalkyl group in the latter being selected from the group consisting of cyclopentyl, methylcyclo pentyl, cyclohexyl and methylcyclohexyl and the alkyl substituent has not more than four carbon atoms and is attached to the alpha-carbon atom of the cycloalkyl group, which is the carbon atom joined to the phenyl radical.

2. The composition of claim 1 wherein said cycloalkyl compound is bis-(Z-hydroxy-3-alpha-methylcyclohexyl-5- 3. The composition of claim 1 wherein said cycloalkyl bis-(2-hydroxy-3-alpha-gamma-dimethylcyclohexyl-S -methylphenyl) -methane.

4. The composition of claim'l wherein said cycloalkyl compound is bis-(2-hydroxy-3-alpha-n-butylcyclohexyl-S- 5. The composition of claim 1 wherein said cycloalkyl compounds is the magnesium salt of bis-(2-hydr0xy-3- adph a-methyl-cyclohexyl-S-methylphenyl) -methane.

6. The composition of claim 1 wherein the rubbery F. Bis (2 hydroxy 3 c ethylcyclohexyl methylphenyl)-methane. G. Bis (2 hydroxy 3 a'y dimethylcyclohexyl 5 methylphenyl)-methane.

No antioxidant methylphenyD-methane. I. Bis (2 hydroxy 3 a n butylcyclohexyl 5 methylphenyl)-methane. 1 compound d J. No antioxidant. K. Bis (2 hydroxy 3 oc'y dimethylcyclohexyl 5 methylphenyl -methane. methyl-phenyl -methane.

L. No antioxidant. M. Magnesium salt of bis-(2-hydroxy-3-a-methylcyclohexyl-S-methylphenyl)-methane.

E F G H I K L M Tensile strength (Kg/sq. cm.):

Unaged 135 186 179 187 After bomb ageing O.8 days... pr 88 At 70 0., 300 p. s. i.12 days pr 79 77 p In oxygen-16 days pr 54 68 After Geer oven2 weeks 66 83 85 Ageing-4 weeks 44 75 83 At 70 O.-6 weeks After Geer oven-16 hours 46 60 67 Ageing-32 hours 33 52 '55 39 At 0.-48 hours 23 38 39 Shade after outdoor exposure po 0 c vpc In the table the followingabbreviations are used, viz: pr=perished, p=pale, c=cream, and v=very.

Mixes E, F and G were exposed for 13 weeks, H, I, L and M for 4 weeks and J and K for 8 weeks.

What we claim is:

l. A composition comprising a rubbery polymer selected from the group consisting of natural rubber, butadiene synthetic rubber, and chlorobutadiene synthetic rubber having incorporated therein at least one cycloalkyl compound selected from the group consisting of bis-(2-hypolymer is in the form of a stabilized synthetic rubber 

1. A COMPOSITION COMPRISING A RUBBERY POLYMER SELECTED FROM THE GROUP CONSISTING OF NATURAL RUBBER, BUTADIENE SYNTHETIC RUBBER, AND CHLOROBUTADIENE SYNTHETIC RUBBER HAVING INCORPORATED THEREIN AT LEAST ONE CYCLOALKYL COMPOUND SELECTED FROM THE GROUP CONSISTING OF BIS-(2-HYDROXY - 3 - ALPHA - ALKYL - CYCLOALKYL - 5 - METHYLPHENYL)METHANES AND THE BASIC AND NORMAL ALUMINUM, BARIUM, CALCIUM, MAGNESIUM, STRONTIUM AND ZINC SALTS OF SUCH METHANES, THE CYCLOALKYL GROUP IN THE LATTER BEING SELECTED FROM THE GROUP CONSISTING OF CYCLOPENTYL, METHYLCYCLOPENTYL, CYCLOHEXYL AND METHYLCYCLOHEXYL AND THE ALKYL SUBSTITUENT HAS NOT MORE THAN FOUR CARBON ATOMS AND IS ATTACHED TO THE ALPHA-CARBON ATOM OF THE CYCLOALKYL GROUP, WHICH IS THE CARBON ATOM JOINED TO THE PHENYL RADICAL. 